Desulfurization of fluid coke with oxygen and hydrogen



Oct. 18, 1955 R. B. MASON ET AL 2,721,169

DESULFURIZATION OF FLUID COKE WITH OXYGEN AND HYDROGEN Filed May 21, 1954 COKING ZONE OXIDIZING ZONE (650|OOO"-F) COKE HYDROGEN TREATING ZONE (PREFERABLY |400-I500F) DESULFURIZED RALPH B. MASON, CHARLES N. K|MBERL|N,JR. INVENTORS ATTORNEY United States Patent ()1 1 2,721,169 DESULFURIZATION F FLUID COKE WITH OXYGEN AND HYDROGEN Ralph B. Mason and Charles N. Kimberliu, Jr., Baton Rouge, La., assignors to Esso Research and Engineering Company, a corporation of Delaware Application May 21, 1954, Serial No. 431,412 9 Claims. (Cl. 202-31) This invention relates to improvements in desulfurizing and activating coke particles containing high percentages of sulfur. More particularly, it relates to the desulfurization of high sulfur petroleum coke particles from the fluid coking process by subjecting the coke particles to low temperature oxidation with an oxygen-containing gas followed by a hydrogen treatment both at controlled temperatures. It also relates to an improved low temperature oxidation conditioning treatment of these fluidized coke particles.

There has recently been developed an improved process known as the fluid coking process for the production of coke and the thermal conversion of heavy hydrocarbon oils to lighter fractions. The fluid coking unit consists basically of a reaction vessel or coker and a heater or burner vessel. In a typical operation the heavy oil to be processed is injected into the reaction vessel containing a dense turbulent fluidized bed of hot inert solid particles, preferably coke particles. Uniform temperature exists in the coking bed. Uniform mixing in the bed results in virtually isothermal conditions and effects instantaneous distribution of the feed stock. In the reaction zone the feed stock is partially vaporized and partially cracked. Product vapors are removed from the coking vessel and sent to a fractionator for the recovery of gas and light distillates therefrom. Any heavy bottoms is usually returned to the coking vessel. The coke produced in the process remains in the bed coated on the solid particles. Stripping steam is injected into the stripper to remove oil from the coke particles prior to the passage of the coke to the burner.

The heat for carrying out the endothermic coking reaction is generated in the burner vessel. A stream of coke is transferred from the reactor to the burner vessel employing a standpipe and riser system; air being supplied to the riser for conveying the solids to the burner. Sulficient coke or carbonaceous matter is burned in the burning vessel to bring the solids therein up to a temperature suflicient to maintain the system in heat balance. The burner solids are maintained at a higher temperature than the solids in the reactor. About of coke, based on the feed, is burned for this purpose. This may amount to approximately to of the coke made in the process. The unburned portion of the coke represents the net coke formed in the process and is withdrawn.

Heavy hydrocarbon oil feeds suitable for the coking process are heavy or reduced crudes, vacuum bottoms, pitch, asphalt, other heavy hydrocarbon petroleum residua or mixtures thereof. Typically, such feeds can have an initial boiling point of about 700 F. or higher, an A. P. I. gravity of about 0 to 20, and a Conradson carbon residue content of about 5 to wt. percent. (As to Conradson carbon residue see ASTM Test D180-52.)

It is preferred to operate with solids having an average particle size ranging between 100 and 1000 microns in diameter with a preferred average particle size range between 150 and 400 microns. Preferably not more than 5% has a particle size below about 75 microns, since small particles tend to agglomerate or are swept out of the system with the gases.

The method of fluid solids circulation described above is well known in the prior art. Solids handling technique is described broadly in Packie Patent 2,589,124, issued March 11, 1952.

2,721,159 Patented Oct. 18, 1955 Fluid coking has its greatest utility in upgrading the quality of low grade vacuum residua and pitches from highly asphaltic and sour crudes. Such residua frequently contain high concentrations of sulfur of 3% or more and the coke product produced from these high sulfur feeds are also high in sulfur content. In general the sulfur content of the coke product from the fluid coking process may be in the range of 1 to 2 times the sulfur content of the residum feed from which it is produced. The sulfur content of coke from sour residua may range from 5 to 8% sulfur or more. The high sulfur content of the coke product poses a major problem in its eflicient utilization. For most nonfuel or premium fuel uses a low sulfur content coke, below about 3 wt. percent sulfur, or at most about 4 Wt. percent sulfur, is required. For example, low sulfur content coke is desired for the manufacture of phosphorous, for the production of calcium carbide, for lime burning in the manufacture of soda ash or other alkalis, for various metallurgical application, for the production of electrode carbon for various electrochemical applications such as the manufacture of aluminum and the like. Heretofore the sulfur content of high sulfur cokes from various sources has been reduced by a high temperature calcination in the range of about 2100 F. to

ice

. 2800" F. in the presence of various gases such as flue gases,

nitrogen, hydrogen, steam, and the like. However, this method of reducing sulfur is undesirably expensive due to the high temperatures required and the necessity of employing expensive refractory materials in the construction of the calciners. The sulfur content of cokes has also been reduced by treatment with hydrogen gas at somewhat lower temperatures in the range of 1200 to 1800 F. However, this method of treatment is also undesirably expensive due to the slow rate at which the sulfur is removed and the long treating time required to obtain the desired low level of sulfur content when starting with a high sulfur content raw coke.

- The problem is even further complicated in the treatment of fluid petroleum coke because of the mentioned possibly higher than normal sulfur content from high sulfur feeds. In addition, the fact that the coke particles are built up by the continuous superposition of layers makes for much greater difficulty in sulfur removal without decreasing the coke yields.

The invention provides an improved process for desulfurizing coke, particularly high sulfur containing fluid petroleum coke particles wth gaseous reagents. The process comprises subjecting the coke particles in the form of a dense turbulent fluidized bed to a low temperature oxidation treatment with an oxygen-containing gas followed by a controlled hydrogen treatment. The sulfur content is consequently reduced to below 3 weight per cent by this treatment. As will be shown below, treating conditions outside those stipulated result in inferior results as do treatments with either hydrogen or oxygen alone.

The treatment with the oxygen-containing gas is conducted at a temperature of 6001000 F., preferably 650850 F. This low temperature oxidation treatment is preferably carried out while the coke particles are in the form of a dense turbulent fluidized bed. While it may be possible to effect the desired result of the low temperature oxidation by treatment of a fixed bed or moving fixed bed of coke with an oxygen-containing gas, the problem of removing the heat of reaction from a fixed bed, except in the case of very small fixed beds, makes the control of temperature very difiieult in this type of operation. In contrast to a fixed bed, the temperature of oxidation is very easily controlled when oxidizing coke in a fluid bed by treatment with an oxygen-containing gas. The temperature may be controlled by means of coils immersed in the fluid bed. It is in- 3 H deed surprising that these low temperature levels are necessary and that higher temperatures produce worse results as the reverse would normally be expected. The oxygen-containing gas can be atmospheric air or air enriched with oxygen at atmospheric or superatrnospheric pressures. The time of the oxygen treatment can range broadly within the range of 15 minutes to 50 hours as will depend on the temperature and the oxygen concentration and pressures. When conducting the pre-oxidation at the higher temperatures of about 800-.1000 within the operable range, it may be preferred to employ air deficient in oxygen such as air diluted with steam, nitrogen, vflue ,gas, or the like. exit gases from the oxidation may be .recycled to the oxidation zone; The best control feature within these 7 ranges .is .the yield loss of the coke subjected to the oxidation. The conditions are controlled withinthe preceding ranges so that amaximum yield loss of 20 weight percent, preferably 10 weight per cent, or conversely a minimum yield of '80., preferably 90 weight per cent, is obtained. For certain special applications of the low temperature oxidized coke or .desulfurized coke it may be desirable to oxidize to a greater extent, for example, to a yield of 50% to 60%; however, for most .cases yields below about 80% are uneconomical. The low temperature oxidation is ,a non-catalytic reaction and it is not necessary to add a catalyst to the system. In the low temperature oxidation a part of the coke, 2% to 20% or'more, preferably 3% to 10%, is converted to .its ultimate combustion products of carbon .dioxide and water. Small amounts of carbon monoxide and sulfur dioxide are also produced as combustion products in the low temperature oxidation. Those skilled in the art will be able to easily obtain the desired sulfur .reduction by combining the oxidation treatment with the hydrogen treatmentdescribed hereafter;

The :hydrogen treatment is conducted at a tempera- If desired a :part of the ture of about ;.l200l700 E, preferably at .1400?-- l500 Feat atmospheric pressures or above. The coke is contacted at suitable temperature and pressure with a fiowof hydrogen which sweeps the hydrogen sulfide productout of the hydrogen treatment zone. The minimum flow of hydrogen utilized is about 100 'v.. /v. [hr. (volumes of :hydrogen per :volume 'of coke per hour). If desired :the hydrogen leaving the hydrogen treatment zone -:may be scrubbed or, otherwise treated by known means to removeyor recover hydrogensulfide and recycled -.to the hydrogen treatment. zone. The treatment of .the -preoxidizedcoke with hydrogen is a non-catalytic process and it is'not necessary to add a catalyst to zthe system; The time of treating-is in the range of .10 minutes to about .10 :hours, although the time is not critical In contrast with the preceding oxygen treatment, the hydrogen treatment :may be advantageously conducted. while ,the .coke particles are in a fixed bed or .a'mo'vingfixed :hed. Since .the heat of reaction in the hydrogen .treatmentis relatively small and the con: .trol of temperature .is less critical than in the'oxygen treatment, a fixedbed may 'be employed. However, a fluid bed typeoperation may also be vemployedfor the hydrogen treatment. The choice of the method of contacting the coke with hydrogen will often depend upon the type of equipment available for this operation.

' The hydrogen-containing gas can be obtained from the gas produced in the coker after removal of most of thehydrocarbons formed in 'the coking operation. Other sources of hydrogen includethe pure gas or the tail ,gas from a hydroforrner. 'The hydrogen-containing 'gasfis preferably treated 'in the conventionalmanner to remove hydrogen 'sulfide and other sulfur-containing "compounds before use.

"This invention will be betterunderstood 'byreference to the flow diagramshown in'the drawing.

In *the drawing, numeral "1 represents a reactor constructed of suitable materials for operation at temperathe reactor through line 2.. They can be'fed .directlyfrom the fluid coke reaction system or from a final product coke inventory. The temperature of fluid bed 6 is main- .tained at the desired level Within the range of 600l000 R, preferably 650 850 :F., by means of cooling'coil 6a immersed in fluid bed 6. The flue gas comprising nitrogen, water, carbon dioxide, small amounts of carbon monoxide and sulfur dioxide, and unconsumed oxygen passes upwardly through the .bed and is removed 4mm the vesselvia line 5 after passing through cyclone4-from which solids are returned to the bed via dipleg 14.

A'stream of oxidized coke particles is removed -=from the oxidizing zone via line 8 into hydrogen-treating zone 10. The temperature is maintained within apreferred range of 1400-I500 F. The drawing shows the oxidized coke particles in the form of a falling-or descending fixed bed 12 in hydrogen-treating zone 10; however, if preferred, hydrogentrea-tment zone 10 may comprise one or more fluid beds of the oxidized coke particles. Hydrogen-containing gas enters the vessel 10 through line 9. The gasesleaving through line 13 contain hydrogen sulfide and may contain some methane and'other hydrocarbon gases in addition to unconsumed hydrogen. The low temperature oxidized coke entering hydrogen treating zone 10 by line 8 may be preheated -to atemperature about 50 to 200 F. below the desired hydrogen-treating temperature by passage through'heating zone 16. Upon entering zone 10 the coke is further heated to the desired hydrogen treating temperature by a momentary strongly exothermic reaction which occurs when the low temperature oxidized coke is'first contacted by hydrogen. Whilethis exothermic reaction of short dura-' tion is 'not fully understood, it'maybe the combination of hydrogen with oxygen adsorbed on the coke surface.

Heat may also be supplied to hyline 9 by passage-through heating zone 15. Heating-zone 15 may comprise -a coil in a furnace, or a heat exchanger for recovery of heat from desulfurized coke in line 11, or other heating means. When coke bed 12 comprises a fluid- -bed, heat may also be supplied to hydrogen treating zone '10 by means of a heating 'coil immersed inbed 12. Hot combustion gases may be passed through the heating coil to supply heat. Desulfu-rized coke product is removed-through line -1-1.

The following examples further show the advantages of this invention.

EXAMPLE "1 "To illustrate a prior art process for the removal o'f sulfur from coke and to obtain data fo r'comparison to show the advantages of the process of the present in vention, samples of raw coke were treated with hydrogen atseveral temperatures without prior preoxidation-at low temperature. T he-rawcoke employed comprised 7-weight The .hydrogen treatment was conducted at atmospheric cated temperatures. These data show that over the range of -1000 -to 2400 F. the rate 'of sulfur removal from the-raw coke is-most rapid at about'-1 3'00 F. The data 6 EXAMPLE 3 To illustrate the improvement in desulfurization at tained by the combined low-temperature-oxidation and hydrogen treatment, samples of coke containing 7 weight per cent sulfur from fluid coking of Hawkins residuum were pre-oxidized and then treated with hydrogen. The oxidation was accomplished by treatment of a fluid bed Table I.Treatment of raw cake (7% S) with hydrogen [Atmospheric pressure, 1,500 v./v.lhr.]

Column 1 2 3 4 5 I e I 7 8 Temperature,F 1,000 1,200 1,300 1,400 1,600 1,800 2,100 2,400

Percentsremaining after 0.5 Hr 6.8 5.9 5.6 5.8 5.9 6.7 6 5 4.9 Percent Srematning atterlHr 6.7 5.5 5.1 5.4 5.6 Percent Sremaim'ng after2Hrs. 4.9 4.4 4.9 5.3 PercentSremaintng afterfiHrs 4.1- 3.5 4.6 5.2 6.7 6.4

EXAMPLE 2 of coke with air at atmospheric pressure at the desired To illustrate the efiect of low temperature oxidation temperatuie for the 9 of requlred to i fl without hydrogen treatment on the properties of coke, deslred yleld of pfe'oxldlzed coke Th6 pie'oxldlzed Samples of coke containing 7 weight per cent Sulfur coke was treated with hydrogen at atmospheric pressure from fluid coking of Hawkins residuum were oxidized at a temperature of 1300 a a hydrogen flow rate at various temperatures to various yield levels. The oxof .3? ldsoo L g- 1 1 22 ed ed 3 i idation was accomplished by treatment of a fluid bed of Dre-OX1 lze a e 5 WS e c n en Coke with air at atmospheric pressure at the desired of the hydrogen treated coke after various time intervals temperature for the period of time required to give the oflglydr'ogen F i 1 d d 1 1 f th desired yield of oxidized coke. The data obtained are or companson a a are me u e co mu shown in Table H. For comparison data are also shown table forth? hydrogen treatment of raw (un'pre'oxldlzed) for the raw unoxidized coke and for a sample of'coke coke? and 9 ,column 8 E treatmwft, oi Oxidized at 11000 R Comparison of the data in COL coke pre-oxidized at 1100 F., which s outside the critical umns 2, 3 4, 5, 6 and 7 with column 1 clearly Shows temperature range for desulfurization. Comparison-0f that oxidation within the preferred temperature range 40 the data of columns? 4, 6, column of 650 to 850 F. results in a slight reduction of the 1 Clearly Shows the Improved desulfurllahoh when ysulfur content, a large increase in the surface area, and drogen treating coke pre-oxidized in the preferred tema substantial increase in the real density of the coke. perature range of 650 to 850 F. The data of column On the other hand, a comparison of the data in column 8 show that hydrogen treatment of coke pre-oxidized at W1th Fohlmn 1 Shows that OXldatlOIl f 9" 0 Which 1100 F. is only slightly better, if any, for sulfur reis outside the range of the present invention, actually moval h hydrogen treatment f raw k P id causes an In sulfur content of f coke due tion at 1100" F. is outside the critical temperature range to the preferential burning of carbon relative to sulfur for Sulfur removaL Comparison of columns 2 '5 g g g i gf gg fi i i ig i g l g f gg 22:3? and 7 show that at constant, or nearly constant, levels of i coke comparisog of the data in columns of yield the lower the temperature of pre-oxidation within 3 5 and 7 Show that in g e me I 31 the lower the oxida: the preferred temperature range the better the desulfurization temperature within the preferred range, the greater upon Subsequent treatment wlth hydrogen. m tha improvement in coke properties Comparison of parison of columns 3 and 4 and of columns 5 and 6 columns 3 and 4 and of Columns 5 and 6 Show that show that the degree of improvement attainable at the in general, the lower the yield upon oxidation, the greater temperatures Wlthhl the Preferred range y the improvement in coke properties. However, in general, it is preferred to oxidize to yields greater than about be attained at the higher temperatures within the preferred range by taking lower pre-oxidized coke yields, again withii the specified range.

Table II-Propertz'es of low temperature Oxidized Column 1 2 3 4 5 6 7 8 Oxidation Conditions:

Temperature, F N one 650 700 700 750 750 850 1, Time, Hrs 0 16 5 23 2 4. 2 1. 5 1 Yield, wt. percent 100 93 93 55 94 80 91 93 Properties of Oxidized Cok Wt. Percent Sulfur. 7 6.7 6. 7 5.6 6.3 6.2 6.4 7. 2 Surface Area, M /g 5 136 133 358 98 199 83 2 True Density 1. 55 1. 63 1. 63 1. 88 1. 73 1. 61 1. 60

'rRE-oxmAm V Impa amre,F .None. .650. 700 200 750 750 850 1,100v Yield, Wt. Percent 100 93 93 62 94 so 91 93 HYDROGEN TREATMENT AT l,300 F. AND 1500 v./v.fhr.

Percentsremaining after 0.5 Hr 5.6 3.3 3.3 2.8. 4.4- 3.6 4.2. 5.3 Pereentsremainlng atter1Hr 5.1 2.6 2.9 2.4 3.8 28 3.6 4.6 PeroentSremaining after2Hrs. 4.4 2.0 2.3 2.2 -3.2 72.3" 3.0 4.4) PercentSremainingatter4Hrs.... 3.7 1.7 2.2 2.0 2-5. V2.1. 2.8. 3t6.

EXAMPLE 4 Table .V ..Desulfurization of Coke 7% s Samples of coke containing 7 weight per cent sul fur PBETQXIDK-HQN from fluid coking of Hawkins residuum were pre-oxidized C fq and then treated with hydrogen. The oxidation was acoumn complished by treatment of a fluid bed of coke with '1 F a a t d i e tem ure for t p r q i Yi V g 1 ercent-; ii 33 33 23 quired to give ,the' desiredyield of 'pre-oxidized coke. The. pre-oxidized coke was treated with hydrogen at HYDROGEN TREATMENT various temperatures at a hydrogen .flow rate of about .m-

- 1500 v./;v./hr. employing a fixed 'bedof the pre-oxidized g g t H Ab t 1,402 1, 2. 1,309 1, g g 9. 3 v coke Table Iv shows the i f i of the hy 3,0 Hydrogen Rate,v ./v./hr 1,500 4,550 1, 500 4,559 4mg treated coke afmr 9 9i PercentSremainingafterOjHr- 2.1 "1.9 2.3 1.0 drogen treatment. The data show that the' sulfur reer e tn aetna el sa t rkH -1 1,135 4 moval from the pre-oxidized coke is most favorable when i. the hydrogen treatment is conducted inthe preferred c cu fi 9-?i 3 .I .1 -P IQ- emperature range of about to 5.00 F. This is In .-summary,;all the foregoingdata .show .thatthesul. in contrast to raw 'co'ke which, as shown in Table is fur content can be .reduced'below '3. weight :per cent and desulfurized rnorereladily'by hydrogen treatment at about that, i;.e.,, fr om"1 .to:2% weightpereent bythe process .of 1300-" 'F., even thoughunder this most favorable eonthis invention. 1 dition the-raw or-un-pre-oxidized-- coke is desul-furized -In .order. to express this: information-more 'fully the With-extreme slowness. 1 40 fqllowingconditions of.operation .of the various fluid cok r y a ing components :are set forth below.

FEE-OXIDATION 1' Y Broad Preferred V Bgnge Range Y 1 gem er tg e f eon-1,000 1 I ressure mosp I 1.5-2 Temperature )F 7. Q59 650 150 750 .750 Y r YmdVWt'vPmenL 93 M80 so Superficial Velocity of Fluldizlng Gas:- ojrlzo HYDsKO-G-ENTREATMENT ATi,500.V;/V./H RJ r j DIT IQN S IN Jar, 5,:292; 11,20 2. ng g; 1,302 g 216 1154 2:8 212 -2I1 RereentSgenrainingatteflI-Ire, ,20. 1.1 2.3 1.9 19 I Pereeutsremaimugafter'firs; 1.7 1.).9 2.1 1.7 La -w w- WW. 9.0

' 1 Tempergture,-F -'1, 050-1,-600' -1,1oo -1,-20n

. o .suve gi Yeloc r EXAMPLE 5 i- Samples of coke containing 7 weight per cent sulfur from fluid coking of Hawkins residuum were pre-oxidized and then treated with hydrogen. complished by treatment of a fluid bed of coke with air at the desired temperature for a period of time required to give the desired yield of pre-oxidized coke. The preoxidized coke was treated with hydrogen at various ternperatures and at 1 atmosphere and at 3.4 atmospheres pressure absolute employing a fixed bed of preo'xidiz'ed coke. The hydrogen flow rate was adjusted to v:give .approximately the same rate of displacement of gases ;in the reactor at the two levels of pressure. Table V shows the sulfur content of the hydrogen treated coke after onehalf and one hour of hydrogen treatment.

pressure of the treating hydrogen gives a slight increase in the rate of sulfur removal.

The oxidation was ac-;

As stated before, the process of this invention is particularly suitable and preferred for the desulfurization of containing smaller quantities of sulfure Several of treating with an oxygen containing v gas .foll owed by:

I drogen can b 'eemployed if desired.

qmp son of columns 1 and 2 show that an increase in the partial $9. iun e stpod t this. imient ongis m s to the spes fie examp es .rrhieh haye been .oflered merely as illustrations and that modifications may be made without departing from'the spirit of the invention.

What is claimed is:

1. A process for desulfurizing coke particles containing a high percentage of sulfur, which comprises the steps of treating the coke particles with an oxygen-containing gas at a temperature in the range of 600 to 1000 F. for from 15 minutes to 50 hours so as to obtain a minimum coke yield of 80 weight per cent and treating the thus oxidized coke with hydrogen at a temperature in the range of 1200 to 1700 F. with a minimum of 100 v./v./hr. of hydrogen whereby the sulfur content of the coke is reduced to below 3 weight per cent.

2. A process for desulfurizing coke particles containing a high percentage of sulfur, said particles having been produced by contacting a heavy petroleum oil coking charge stock at a coking temperature with a body of coke particles maintained in the form of a dense turbulent fluidized bed in a reaction zone, wherein the oil is converted to product vapors and carbonaceous solids are continuously deposited on the coke particles, removing product vapors from the coking zone; burning a portion of coke particles removed from the coking zone in a separate burning zone to increase the temperature of said fluidized particles, returning a portion of the heated coke particles from the burning zone to the coking zone and withdrawing product particles which comprises the steps of treating the coke particles with an oxygen-containing gas at a temperature in the range of 600-l000 F. for from 15 minutes to 50 hours so as to obtain a minimum coke yield of 80 wt. percent and treating the thus oxidized coke with hydrogen at a temperature in the range of 1200-1700 F. with a minimum of 100 v./v./ hr. of hydrogen whereby the sulfur content of the coke is reduced to below 3 weight per cent.

3. The process of claim 2 in which the coke particles being treated with an oxygen-containing gas are in the form of a dense turbulent fluidized bed.

4. The process of claim 3 in which the oxygen-contain ing gas treating step is conducted at a temperature in the range of 650 to 850 F. so as to obtain a minimum coke yield of 90 weight per cent.

5. The process of claim 4 in which the hydrogen- 10 treating step is conducted at a temperature in the range of 1400 to 1500 F. for from 10 minutes to 10 hours.

6. A process for conditioning and improving the surface characteristics of coke particles containing a high percentage of sulfur, said particles having been produced by contacting a heavy petroleum oil coking charge stock at a coking temperature with a body of coke particles maintained in the form of a dense turbulent fluidized bed in a reaction zone, wherein the oil is converted to product vapors and carbonaceous solids are continuously deposited on the coke particles; removing product vapors from the coking zone; burning a portion of coke particles removed from the coking zone in a separate burning zone to increase the temperature of said fluidized particles, returning a portion of the heated coke particles from the burning zone to the coking zone and withdrawing product particles which comprises treating the product coke particles with an oxygen-containing gas at a temperature in the range of 600-1000 F. for from 15 minutes to hours.

7. The process of claim 6 in Which the minimum coke yield obtained is weight per cent.

8. The process of claim 7 in which the oxygen-containing gas treating step is conducted at a temperature in the range of 650 to 850 F. so as to obtain a minimum coke yield of Weight per cent.

9. The process of claim 6 in which the product coke particles being treated with an oxygen-containing gas are in the form of a dense, turbulent, fluidized bed.

References Cited in the file of this patent UNITED STATES PATENTS 2,595,366 Odell et a1 May 6, 1952 2,684,930 Berg July 27, 1954 2,693,999 Reed NOV. 9, 1954 2,694,035 Smith et a1. Nov. 9, 1954 FOREIGN PATENTS 676,494 Great Britain July 30, 1952 690,791 Great Britain Apr. 29, 1953 

2. A PROCESS FOR DESULFURIZING COKE PARTICLES CONTAINING A HIGH PERCENTAGE OF SULFUR, SAID PARTICLES HAVING BEEN PRODUCED BY CONTACTING A HEAVY PETROLEUM OIL COKING CHARGE STOCK AT A COKING TEMPERATURE WITH A BODY OF COKE PARTICLES MAINTAINED IN THE FORM OF A DENSE TURBULENT FLUID IZED BED IN A REACTION ZONE, WHEREIN THE OIL IS CONVERTED TO PRODUCT VAPORS AND CARBONACEOUS SOLIDS ARE CONTINUOUSLY DEPOSITED ON THE COKE PARTICLES, REMOVING PRODUCT VAPORS FROM THE COKING ZONE; BURNING A PORTION OF COKE PARTICLES REMOVED FROM THE COKING ZONE IN A SEPARATE BURNING ZONE TO INCREASE THE TEMPERATURE OF SAID FLUIDIZED PARTICLES, RETURNING A PORTION OF THE HEATED COKE PARTICLES FROM THE BURNING ZONE TO THE COKING ZONE AND WITHDRAWING PRODUCT PARTICLES WHICH COMPRISES THE STEPS OF TREATING THE COKE PARTICLES WITH AN OXYGEN-CONTAINING GAS AT A TEMPERATURE IN THE RANGE OF 600* - 1000* F. FOR FROM 15 MINUTES TO 50 HOURS SO AS TO OBTAIN A MINIMUM COKE YIELD OF 80 WT. PERCENT AND TREATING THE THUS OXIDIZED COKE WITH HYDROGEN AT A TEMPERATURE IN THE RANGE OF 1200* - 700* F. WITH A MINIMUM OF 100 V./V./HR. OF HYDROGEN WHEREBY THE SULFUR CONTENT OF COKE IS REDUCED TO BELOW 3 WEIGHT PER CENT. 